Multi-circuit rotary electrical connector



July 30, 1963 A. c. SCOTT MULTI-CIRCUIT ROTARY ELECTRICAL CONNECTOR 2Sheets-Sheet 1 Filed Dec. 7, 1959 IOc loc

July 30, 1963 A. c. SCOTT 3,099,503

MULTI-CIRCUIT ROTARY ELECTRICAL CONNECTOR Filed Dec. 7, 1959 2Sheets-Sheet 2 United States Patent 3,099,503 MULTl-CIRCUIT ROTARYELEQTRICAL CONNECTQR Alec C. Scott, New Hyde Park, N.Y., assignor, bymesne assignments, to Aerollex Laboratories Incorporated,

New York, N.Y., a corporation of Delaware Filed Dec. 7, 1959, Ser. No.857,639 7 Claims. (Cl. 339-2) This invention relates to multi-circuitrotary electrical connectors and particularly to such connectorsdesigned for a limited range of relative rotation between stator androtor assemblies.

In many electromechanical systems it becomes necessary to bridge arotary mechanical joint with a number of electrical circuits carryingpower or sensing information, or both. For example, in conventional gyrosystems it is necessary to transmit across the pivots of both the innerand outer gimbal rings power for driving the gyro motor and, inaddition, it is desired to transmit a number of sensing and controlsignals developed by the gyro back across the pivots to the electricalsystem of which the gyro is a part.

Heretofore it has been customary tobridge such rotary joints or pivotsby means of conventional slip rings and co-operating sliding brushes orcontacts or, in the event the range of relative rotation is limited asin a gyro, by flexible connectors secured directly to both of therelatively moving parts. The former arrangement has the many well-knowndisadvantages of sliding contacts, such as a relatively high andunstable electrical resistance, a relatively high electrical noiselevel, etc. The latter arrangement has the disadvantage of possiblefailure from fatigue after a relatively low number of operating cyclesand a requirement of appreciable torque for flexing the connectors,particularly where a large number of circuits must be bridged across therotary joint.

It is an object of the invention, therefore, to provide a new andimproved multi-circuit rotary electrical connector which obviates one ormore of the foregoing disad vantages of prior rotary connectors of thisgeneral type.

It is another object of the invention to provide a new and improvedmulti-circuit rotary electrical connector which has one or more of thefollowing characteristics: extremely low operating torque; operationover a large number of cycles without failure from fatigue; and freedomfrom any sliding or relatively moving contacts.

It is another object of the invention to provide a new and improvedmulti-oircuit rotary electrical connector which is readily adapted forstacking of a number of elements where the number of circuits to bebridged across the rotary joint is larger than can be readilyaccommodated by a single connector assembly.

In accordance with the invention, a unitary multi-circuit rotaryelectrical connector comprises a pair of members of insulation material,one of such members being in the form of a disc, one of such membershaving provisions for supporting the other member for relative rotation,and one of such members having a central aperture substantially coaxialwith the axis of relative rotation. The connector also comprises aplurality of flexible electrical conductors each disposed with its outerend anchored to a fixed point on the disc member near its periphery andwith its inner end anchored to a fixed point on the other of the membersnear the axis of relative rotation of the members, a portion of each ofthe conductors extending axially through said aperture.

For a better understanding of the present invention, together with otherand further objects thereof, reference is had to the followingdescription taken in connection with the accompanying drawings, whileits scope will be pointed out in the appended claims.

Patented July 30, 1963 Referring now to the drawings:

FIG. 1 is a plan view of a multi-circuit rotary electrical connectorembodying the invention with the cover removed;

FIG. 2 is an exploded longitudinal sectional view of the connector ofFIG. 1;

FIG. 3 is a longitudinal sectional view of a stack of four multi-circuitrotary electrical connectors of the type represented in FIGS. 1 and 2;while FIG. 4 is a plan view of a modified form of connector which atpresent is considered to be the preferred embodiment of the invention.

Referring to FIGS. 1 and 2 of the drawings, there is represented amulti-circuit rotary electrical connector embodying the invention. Thisconnector comprises a pair of members of insulation material 10 and 11mounted for relative rotation, each having a central aperturesubstantially coaxial with the axis of relative rotation. For example,the member 10 has a central hub 10a through which extends an aperture1017, while the other member 11 is in the form of a disc having acentral aperture 11a which is journaled on the hub 10a to provide forrelative rotation of the members.

The disc member :11 is provided with a plurality of ribs 12 ofinsulation material disposed on one face thereof as by being seated inthe grooves 11b in the face of the disc 11. The ribs 12 and the grooves111) in which they are seated extend spirally outwardly from the centralaperture 11a, thereby forming a plurality of spinal channelstherebetween as shown in FIG. 1.

The electrical connector of the invention also comprises a plurality offlexible conductors 13, each disposed in one of the spiral channels withits outer end anchored to a fixed point on the disc 11 at or near itsperiphery as by the terminal pins 14. The inner end of each of theconductors 13 is anchored to a fixed point on the memher 10 near itsaperture. Specifically, as illustrated, all of the conductors 13- extendthrough the aperture 10b of the member 10, while a disc 15 clamps theconductors 13 to the inner face of the hub 10a, the disc 15 being heldin place by any suitable means, such as machine screws 16.

As shown in FIG. 2., all of the conductors 13 extend through theaperture 10b and on to the right, from which suitable connections aremade to the associated electrical system. Each of the conductors 13 maybe a continuous wire from its associated anchor pin 14, continuingthrough the spiral channels and the aperture 10!) or, if desired, it maybe constituted in two parts joined together at or near the hub 10a inany suitable manner, as by soldering, clamping, or the like. Theconductors 13 extending through the central aperture of the connectorare, of course, provided with suitable insulation but preferably theportions of the conductors lying in the spiral channels formed by theribs 12 will be stripped of their insulation, thereby increasing theirflexibility and reducing the required operating torque of the connector.However, for clarity in illustration, in FIG. 2 the portions of theconductors 13 lying in such spiral channels are shown unstripped. Ifdesired, a cup-shaped casing member -17 may be secured .to the basemember 10 in any desired manner, as by machine screws 18 engagingthreaded holes 16c in the member 10. The member 10 may be secured to onememberof the rotary mechanical joint in any desired manner, while aconnecting pin 19 secured to the disc member 11 and projecting throughan aperture 17a of the casing may be attached to the other member of therotary mechanical joint in any suitable manner.

It is believed that the operation of the multi-circuit rotary electricalconnector of the invention will be apparent from the foregoingdescription. Briefly, upon rotation of the member '11 by its connectingpin 19 relative to the base member or vice versa, the flexibleconductors 13 disposed in the spiral channels between the severalinsulating ribs will expand from the position in Which they conformclosely to the adjacent rib in a clockwise direction (FIG. 1) until theymove toward the adjacent rib in the counter-clockwise direction. Therange of relative movement accommodated by this flexing of (theconductors 13' will, of course, depend upon the spacing of theinsulating ribs and the flexibility and clamping of the individualconductors. However, a rotary electrical connector in accordance withFIGS. 1 and 2 has been found satisfactory for bridging the pivot of agyro gimbal ring having a rotation relative to its support of :8".Furthermore, it has been found that such a conhector operates over alife of the order of 1,000,000 cycles before failure from fatigue. Whilethe conductors may be constructed of various types and sizes ofelectrical wire, one embodiment of the invention has utilized strandedcopper Wire comprising seven strands of No. 26 wire with overallinsulation of tetrafluoroethylene, commercially available under thetrade name Teflon.

It will be seen that in the rotary electrical connector described, thereare no sliding contacts in completing the electrical circuits betweenthe two relatively rotatable members; that a minimum operating torque isrequired; and that the device shows freedom from fatigue over a largenumber of operating cycles.

Another advantage of the 'multi-circuit rotary electrical connector ofFIGS. 1 and 2 is that it lends itself readily to the assembly orstacking of a plurality of disc members, such 'as member 11 of FIGS. 1and 2. A unit comprising an assembly of four disc elements is shown inFIG. 3, in which elements corresponding to those of FIGS. 1 and 2 areidentified by the same reference numerals. In this unit the single disc11 of FIGS. 1 and 2 is replaced by four discs '11, 11 and 11", 11".Since each of these discs and its associated spiral ribs and electricalconductors are the .same as shown in FIGS. 1 and 2, the details need notbe further identified. The base member is provided with an elongatedinner hub made up of the portion 20a and a series of interlocked rings21, 22, 23, 24, each of Which clamps the radially extending connectorsof its associated disc member to the next right-hand ring or to the hub20a, as shown. The several rings 21-24, inclusive, are clamped to thehub 20a by any suitable means, such as machine screws 16. The operationof the multi-element rotary electrical connector of FIG. B will beapparent from the foregoing description. It is seen that in thisarrangement, the total number of electrical bridging connections isequal to the number accommodated in a single element multiplied by thenumber of elements in the assembly.

Turning now to FIG. 4, there is represented a modified form of theinvention in which elements corresponding to those of the embodiment ofFIGS. 1 and 2 are identified by the same reference numerals. In thisembodiment the ribs 30 secured to, or moulded as an integral part of,the disc member 31 extend radially outwardly from its central aperturejournaled on the hub of the member 29 and forming therebetween aplurality of radial channels. In this form of the invention, each of theelectrical conductors is in the form of a resilient narrow conductivestrip 32 having one or more U-shaped bends 32a near its outer end. Inthe specific embodiment illustrated, two of these U-shaped bends extendin opposite directions forming an approximate S configuration. The useof conductors of the described configuration permits disposing them inrelatively narrow, sector-shaped slots rather than in the more elaboratespiral slots of the structure of FIGS. 1 and 2, thus permitting the useof a simpler mold. The double bends of spring-like conductors 32, indeflecting, take care of the increased distance between the anchoringpoints of the terminals of the conductors upon relative rotation betweenthe disc member 31 and the base member 29. The conductors 32 are ofmaterial of high conductivity and resilience, for example, berylliumcopper. In this embodiment of the invention, the strips 32, which areseen edgewise in FIG. 4, extend through a peripheral ridge 31a of thedisc member 31, terminating in connection terminals 33. The conductors32 also extend through radial slots in the hub 29a of base member 29,While the axially extending conductors 34 are secured to the inner endsof these strips in any suitable fashion, as by soldering. The embodimentof the invention shown in FIG. 4 has all of the advantages of that shownin FIGS. 1 and 2 and, in addition, has shown capability of operationover an even larger number of cycles before failure from fatigue. Whilethe members 29 and 31 of FIG. 4 may be constructed of any suitablematerial, a tetrafluoroethylene thermosetting plastic commerciallyavailable under the trade name Teflon with integral moulded ribs 30 hasbeen found satisfactory. In one embodiment of the invention, theconductors 32 were in the form of 0.003" by 0.125 beryllium-copperstrips.

While there have been described what are at present considered to be thepreferred embodiments of the invention, it will be obvious to thoseskilled in the art that various changes and modifications may be madetherein without departing from the invention, and it is, therefore,

imed in the appended claims to cover all such changes and modificationsas fall Within the true spirit and scope of the invention.

What is claimed is:

1. A unitary multi-circuit rotary electrical connector comprising: apair of members of insulation material, one of said members being in theform of a disc, one of said members having provision-s for supportingthe other for relative rotation, and one of said members having acentral aperture substantially coaxial with the axis of relativerotation; a plurality of ribs of insulation material disposed on onetace of said disc member and extending outwardly from its centralaperture and forming a plurality of channels therebetween; and aplurality of flexible electrical conductors each disposed in one of saidchannels with its outer end anchored to a fixed point on said discmember near its periphery and with its inner end anchored to a fixedpoint on the other of said members near said axis of rotation, a portionof each of said conductors extending axially through said aperture.

2. A unitary multi-circuit rotary electrical connector comprising: apair of members of insulation material, one of said members being in theform of a disc, one of said members having provisions for supporting theother for relative rotation, and one of said members having a centralaperture substantially coaxial with the axis of relative rotation; aplurality of ribs of insulation material disposed on one face of saiddisc member and extending spirally outwardly from its central apertureand forming a plurality of spiral channels therebetween; and a pluralityof flexible electrical conductors each disposed in one of said channelswith its outer end anchored to a fixed point on said disc member nearits periphery and with its inner end anchored to a fixed point on theother of said members near said axis of rotation, a portion of each ofsaid conductors extending axially through said aperture.

3. A unitary multi-circuit rotary electrical connector comprising: apair of members of insulation material, one of said members being in theform of a disc, one of said members having provisions for supporting theother for relative rotation, and one of said members having a centralaperture substantially coaxial with the axis of relative rotation; aplurality of ribs of insulation material disposed on one face of saiddisc member and extending radially outwardly from its central apertureand forming a plurality of radial channels therebetween; and a pluralityof flexible electrical conductors each disposed in one of said channelswith its outer end anchored to a fixed point on said disc member nearits periphery and with its inner end anchored to a fixed point on theother of said members near said of rotation, .a portion of each of saidconductors extending axially through said aperture.

4. A unitary multi-circuit rotary electrical connector comprising: apair of members of insulation material, one of said members being in theform of a disc, one of said members having provisions for supporting theother for relative rotation, and one of said members having a centralaperture substantially coaxial with the axis of relative rotation; and aplurality of resilient conductive strips each having one or moreU-shaped transverse bends and each disposed with its outer end anchoredto a fixed point on said disc member near its periphery and With itsinner end anchored to a fixed point on the other of said members nearsaid axis of rotation, and a conductor connected to each of said stripsand extending axially through said aperture.

5. A unitary multi-circuit rotary electrical connector comprising: apair of members of insulation material, one of said members being in theform of a disc, one of said members having provisions for supporting theother for relative rotation, and one of said members having a centralaperture substantially coaxial with the axis of relative rotation; aplurality of ribs of insulation material disposed on one face of saiddisc member and extending radially outwardly from its central apertureand forming a plurality of radial channels therebetween; and a pluralityof resilient conductive strips each having one or more U-shapedtransverse bends near its outer end and each disposed in one of saidchannels with its outer end anchored to a fixed point on said discmember near its periphery and with its inner end anchored to a fixedpoint on the other of said members near said axis of rotation, and aconductor connected to each of said strips and extending axially throughsaid aperture.

6. A unitary multi-circuit rotary electrical connector comprising: apair of members of insulation material, one of said members havingprovisions for supporting. the

other for relative rotation, one of said members having a centralaperture substantially coaxial with the axis of relative rotation, andone of said members comprising an assembly of a plurality of discs, eachhaving a plurality of ribs of insulation material disposed on one facethereof and extending radially outwardly from its central aperture andforming .a plurality of channels therebetween; and a plurality offlexible electrical conductors each disposed vvith its outer endanchored to a fixed point on said disc member near its periphery andwith its inner end anchored to a fixed point on the other of saidmembers near said axis of rotation, a portion of each of said conductorsextending axially through said aperture.

7. A unitary multi-circuit rotary electrical connector comprising: apair of members of insulation material mounted for relative rotation,one of said members having a central apertured hub and the other of saidmembers comprising an assembly of a plurality of apertured. discsjournaled on said hub, each having a plurality of ribs of insulationmaterial disposed on one face thereof and extending outwardly from itsaperture and forming a plurality of channels therebetween; and aplurality of flexible electrical conductors each disposed in one of saidchannels With its outer end anchored to a fixed point on said othermember near its periphery and with its inner end anchored to a fixedpoint on said one member near its aperture, a portion of each of saidconductors extending axially through said aperture.

References Cited in the file of this patent UNITED STATES PATENTS874,979 Murphy Dec. 31, 1907 2,702,889 Bareford Feb. 22, 1955 2,739,289Droin Mar. 20, 1956 2,955,271 Dawkins Oct. 4, 1960 FOREIGN PATENTS812,875 Great Britain May 6, 1959 513,269 Italy Feb. 3, 1955

1. A UNITARY MULTI-CIRCUIT ROTARY ELECTRICAL CONNECTOR COMPRISING: APAIR OF MEMBERS OF INSULATION MATERIAL, ONE OF SAID MEMBERS BEING IN THEFORM OF A DISC, ONE OF SAID MEMBERS HAVING PROVISIONS FOR SUPPORTING THEOTHER FOR RELATIVE ROTATION, AND ONE OF SAID MEMBERS HAVING A CENTRALAPERTURE SUBSTANTIALLY COAXIAL WITH THE AXIS OF RELATIVE ROTATION; APLURALITY OF RIBS OF INSULATION MATERIAL DISPOSED ON ONE FACE OF SAIDDISC MEMBER AND EXTENDING OUTWARDLY FROM ITS CENTRAL APERTURE ANDFORMING A PLURALITY OF CHANNELS THEREBETWEEN; AND A PLURALITY OFFLEXIBLE ELECTRICAL CONDUCTORS EACH DISPOSED IN ONE OF SAID CHANNELSWITH ITS OUTER END ANCHORED TO A FIXED POINT ON SAID DISC MEMBER NEARITS PERIPHERY AND WITH ITS INNER END ANCHORED TO A FIXED POINT ON THEOTHER OF SAID MEM-